The primary interest of the power over data transmission is to simplify the cabling for equipment connected to a communication network, and to let allow it to be used without needing to connect it to an additional power source.
In particular, power over data transmission is interestingly applicable in the aeronautics field, using the same cables for electricity and data transmission making it possible to save on weight in an aircraft.
Known in particular is standard IEEE802.3af, published in June 2003, which defines an electricity (“power over Ethernet” or PoE) transmission between a source device and a plurality of powered devices, also called charges, via a connection conveying data over an Ethernet-type network. Standard IEEE802.3af defines the transmission of a DC current on an Ethernet cable, with two or four twisted pairs, capable of transmitting data packets. The power over Ethernet cable has many applications in the field of electronic equipment for the general public and various industrial fields.
The power over Ethernet technology uses transformers or coils to inject electricity into a data transmission cable. One of the constraints that must be respected in order to ensure separation of power transmission and data transmission is to balance the operation of the DC current transmitted in the two conductors of the twisted pair, also called DC balance. Standard IEEE802.3af proposes, in appendix 33 E thereof, a balance circuit that uses resistances with a high value relative to the resistance of the twisted pair used for the transmission of the current. This balance circuit is simple, but has the drawback of a significant loss of power in the resistances.
U.S. Patent application 2006/0115007 describes a method for balancing current between the currents transmitted on a twisted pair, making it possible to compensate an asymmetrical waveform of the current transmitted on the conductors of the twisted pair. This method is sophisticated and involves a large number of components, which makes the balance circuit heavier.
There is therefore a need, in particular for applications in the aeronautics field, to improve the known electricity transmission techniques using data transmission cables.